This invention relates generally to implements for grading land and more particularly to a bogie for use in conjunction with a conventional scraper blade for maintaining the blade at a predetermined level.
It is conventional to grade or flatten uneven terrain by means of a scraper blade drawn by a tractor. Such means is generally effective where there are abrupt humps or pot holes in the ground. Should however there be slight undulations in the ground but otherwise free of humps or potholes, the blade may not be very effective. In fact a blade may actually enlarge slight dips. The reason for this is that as the blade reaches a depression, gravity will cause it to enter the depression and as it does the blade will scrape a layer from the bottom of the depression thereby deepening it.
If the depression is abrupt, such as a pothole, it will be visible to the operator of the tractor and he will be able to lift the blade to prevent the blade from enlarging it. If however the depression is only slight, the operator may not be aware of it and if he fails to lift the blade before the blade reaches it, the blade may enlarge it. As a result, slightly undulating ground may be much rougher after it has been scraped than it was before.
Bogies are known for preventing a blade which is drawn by a tractor from entering a depression. Examples of such bogies are described in a number of U.S. patents including U.S. Pat. No. 2,254,414 to Bowlin; U.S. Pat. No. 2,687,681 to Phenice; U.S. Pat. No. 2,994,977 to Shumaker et al; U.S. Pat. No. 3,090,141 to Shumaker; U.S. Pat. No. 3,092,922 to Knapp et al.; U.S. Pat. No. 4,236,587 to Shader et al.; and U.S. Pat. No. 4,239,251 to Rocksvold.
Known bogies such as those described in the above-noted patents have a number of shortcomings. Some, for example, are only one of a combination of various components. Such combinations may include a blade, four or more wheels, a scoop and so on. Such bogies are not intended for use in conjunction with an existing scraper blade. Other bogies must be attached to all three links of a conventional three point hitch and all three of the links must be operable for the bogie to operate as it is intended. Still others require complicated machinery to adjust the components of the bogie.
The bogie of the invention does not share the short-comings mentioned above. The bogie may be used in conjunction with an existing scraper blade; it does not require that the links of a three point hitch be operable; nor is the means complicated for adjusting the bogie to the conditions of use.
The bogie of the invention controls the up and down movement of a ground-contacting blade attached to a three point hitch at the rear of a tractor. Briefly the bogie comprises an articulated frame having a pair of spaced side rails each having means for connection to a separate lower link of the hitch. An intermediate arm is supported by the side rails and has means for connection to the upper link of the hitch. A castor is mounted for swivelling in a wheel housing. The housing is connected to the intermediate arm. The bogie is equipped with adjusting means for raising and lowering the castor.